Rivers and lakes are popular places for people to relax, play and exercise, and recreational activities like boating, bathing and angling are all well-documented to have positive effects on human well-being. But can the enjoyment of such freshwater ‘ecosystem services’ cause pressures on aquatic ecosystems? And how best can recreational activities be managed to minimise the harm they might cause?

The new MARS-supported study, led by Markus Venohr from IGB Berlin and colleagues, outlines how recreational activities can cause a variety of physical, biological and chemical pressures to freshwaters. Physical pressures can include the noise and waves produced by boats, damage to riparian vegetation and stream banks and beds by human trampling, camping and wading, whilst boats and canoes can stir up bottom sediments, leading to increased water cloudiness (or turbidity).

Biological pressures can include the spread of non-native species due to angling or boating activities, and increased levels of coliform bacteria (e.g. E. coli), as a result of poorly-treated sewage run-off from nearby campsite toilets. Finally, chemical pressures largely stem from increases in nutrient pollution (e.g. from nearby tourist centres), but also include pollution impacts from soap, sunscreen, food particles, human and animal waste, and fuel discharges.

Clearly, there is a geography to such pressures: some are direct and some indirect; some local-scale and others occurring over larger spatial scales. Some activities (e.g. power-boating) will likely create more pressures than others (e.g. wild swimming). Each individual water body will be subject to its own particular socio-ecological ‘cocktail’ of pressures as a result of recreational activities. As Venohr and colleagues put it, the challenge for managers of individual water bodies is to “develop solutions that maximise the well-being of as many people as possible while minimising ecological impacts and therefore reaching ecological quality standards.”

So how can recreational pressures impact ecosystem health and status? Such pressure-impact links are not always fully understood, but have been investigated by a number of recent studies. Motorboat noise has been shown to directly modify fish assemblages, as prey fishes were more easily caught by predators when exposed to noise. Waste water from boats moved between water bodies, and illegal releases of live angling bait and pet fish can both be significant routes for the spread of invasive species across ecosystems (see here (pdf), for example). Recreational angling can impact fish populations in some ecosystems, even after regulations seeking sustainable use, such as catch and release have been implemented (see here and here for example).

Venohr and colleagues propose a new framework for understanding relationships between recreational quality, demand and use, recreational impacts on ecosystem state and function, and ecological and social carrying capacities. They argue that current water management approaches rarely address these relationships, in part due to inadequate information on the dynamics and densities of recreation uses.

The framework has two parts. The first, shown above, shows the relationships between ecosystem quality and recreational demand. It conceptualises that recreational demand will increase or decrease depending on the ecological quality of the freshwater ecosystem. It uses the idea of ‘carrying capacity’ – the limits to sustainable use of an ecosystem – to highlight where ecological damage or human overcrowding of a site may lead to decreasing recreational demand.

The second part of the proposed framework is a ‘multi-loop’ concept, which links ecological quality and recreational quality with responsive ecosystem management. It illustrates how water managers should monitor visitor perceptions of their water body, and how these influence recreational use. These uses influence (and are influenced by) ecological quality, which should be monitored in tandem. Such a linked, responsive approach will allow managers to encourage sustainable recreational uses, which minimise ecological damage, the authors argue.

Markus Venohr outlines the benefits of such an approach, “This framework provides the basis of a next-generation water management approach. It brings together expertise from different disciplines to generate a joint ecosystem assessment attribute – the social-environment carrying capacity of a water body.”

Venohr and colleagues outline the need for novel assessment and monitoring methods to capture the short-term peak dynamics of freshwater recreational activities. They suggest that geotagged social media posts from Twitter, Facebook, Flickr and Instagram have the potential to illustrate recreational activity dynamics across large spatial scales. Geotagged data from social media posts could allow researchers and water managers to analyse how recreational uses of freshwaters varies depending on weather conditions, time of day, season, and site accessibility.

Whilst such digital mapping of human behaviour is increasingly used in business and political strategy, Venohr and colleagues suggest that it holds untapped potential for water management, providing that social media use can first be calibrated to ‘real world’ conditions through the use of interviews, surveys, cameras, flights or drones.

Markus Venohr concludes, “Our study has three key outcomes. First, we found that recreational peak uses of water-bound activities can potentially cause pronounced stress to aquatic ecosystems. Second, we argue that the links between water quality and recreational use has to better understood and conceptualised across larger geographical scales. Finally, we suggest that better assessment of recreation-induced pressures on aquatic ecosystems is needed, both to achieve water management goals and to increase ecological awareness amongst recreational user groups.”

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Features, interviews and analyses on freshwater conservation, science and policy.

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The blog was founded and edited between 2010-14 by the BioFresh project, an EU-funded project that built a global information platform for scientists and ecosystem managers with access to all available data describing the distribution, status and trends of global freshwater biodiversity.

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